Welding technology of Weld Neck Flange
1. Tack welding
Tack welding must be carried out by welders with corresponding qualification certificates. The surface and both sides of the base metal near the weld shall be uniform and smooth without burr, crack, oxide scale, rust, grease, water and other impurities.
The thickness of the positioned welding seam shall not be less than 3 mm, and shall not exceed 2 / 3 of the design weld height, the length shall not be less than 40 mm, the spacing shall be 200-300 mm, and shall be evenly distributed.
2. Welding environment
The wind speed during gas shielded welding is less than 2m / S; Relative air humidity ≤ 80%; The surface of weldment shall be kept dry.
3. Preheating and interpass temperature control
The preheating temperature and interpass temperature shall be determined according to comprehensive factors, such as the chemical composition of steel, the constraint state of joint, the size of heat input, the hydrogen content level of deposited metal and the method used for welding.
4. During welding, the minimum interpass temperature is ≥ preheating temperature, and the maximum interpass temperature is ≤ 230 ℃.
